Persistence of vision is an illusion of  when two images are put together on either side of a single of a piece of paper, for example a candle, the wax being on one side and the light being on the other, when you  flip these images its create the illusion of a single image that would be persistance of vision

Know the reason why were able to see this is because our brain remebers the first part of the image and then we flip over to the other side we still remeber that over part of the image and we see that side as a single  as a single but you would need to keep a fast speed to keep that illusion up.